    function chage(e){
        var text2 = document.querySelector("#zhengshu1").value;
        text2 = Number(text2);
        var text1 = document.querySelector("#zhengshu2").value;
        text1 =Number(text1);
        var a = 0 ;
        switch (e){
            case 'jia':
                a = text2 + text1 ;
                break;
            case 'jian':
                a = text2 - text1 ;
                break;
            case 'cheng':
                a = text2 * text1 ;
                break;
            case 'chu':
                a = text2 / text1 ;
                break;
        }

        document.querySelector("#jieguo").value = a ;
    }
